Crude oil and natural gas are usually obtained from underground formations, from which they are extracted through deep perforations. Generally, the fluid obtained from oil deposits consists of a mixture of oil, gas and brine.
Once the crude oil is extracted, along with gas and water, it is sent to batteries or collecting stations where separation of the different fluids and measuring of the volume produced by the different wells are performed.
Usually, two-phase separators are used for a first, gas-liquid separation, so the gas, after eventual dehydration and sweetening, can be sent for its utilization by means of gas pipelines, while the liquid phase containing oil and water can be sent as such by means of oil pipelines or can undergo a first step of separation in treatment plants before being distributed to oil refineries. It is also possible to use horizontal three-phase separators of the Free Water Knock Out (FWKO) for separating under pressure, gas, water and oil. However, such kind of equipment is usually expensive and very complex in design.
For decades, devices and systems for phase separation for the oil industry have been subject of patents, as can be appreciated for example in U.S. Pat. No. 2,984,360, which discloses a device for separating fluids by means of their differences in density, in particular fluids from an oil field. Such device also has a system that uses a floater for detecting the level of liquid.
U.S. Pat. No. 5,205,310 discloses a method for measuring productivity of marginal oil wells which employs a separator, equipped with level sensors. Although said patent focuses mostly on a separator of oil/water phases, presence of gas at the inlet of the separator is also contemplated. Nevertheless, such device has low-efficiency in terms of cost and investment required and its construction is complex. Additionally, such device uses a water cut measuring system in which, if the cut is too high, measuring becomes difficult because of the working range of the equipment used to this end. This is due to the fact that, in the equipment for measuring mass flow, measuring error is at least 5%, and in cases of elevated water cut, which could be over 95%, the reading performed by the equipment falls within the minimal margin of error of the equipment. This renders the measuring very unreliable. For this reason, it is preferable to separate and measure water alone.
Patent application WO 00/51707 A1 discloses a three-phase separator for a mixture containing a gaseous phase and two liquid phases. Such separator includes a “primary separator” in the inlet flow, allowing separation of gas from the liquid phases. Said primary separator can be any gas-liquid separation device (in particular, a Shoepentoeter type valve) which can be placed in the space of the gaseous phase, as can be seen in the description. The equipment is of the horizontal separator type, the construction of which is complex and burdensome, and the feeding system is included within the separator.
Patent application US 2011/186134 A1 discloses a device for splitting a two-phase flux comprising a “T” joint for separating the fluid. The orientation of the feeding line is substantially vertical, and its interior is conformed for inducing a tangential movement of the phases such as the heavier phase is distributed around the periphery of the feeding line.
Use of two steps of two-phase separation or expensive three-phase separators constitute an obstacle for achieving a cost reduction and originate a permanent need for new, low cost, efficient three-phase separation systems which also have a low impact on the environment.